UPS Static Switch Modulation for Generator Walk-In
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Solution Overview
Problem
UPS systems without a double conversion architecture lack the ability to gradually increase loading of an engine-generator set, leading to potential tripping of protective mechanisms, and existing solutions like EP 1 959 537 A2 are limited in their power transfer management.
Innovation Solution
A UPS system with a static switch and control circuit that modulates power flow from an engine-generator set to an AC output, using an inverter for concurrent power provision, reactive power compensation, and harmonic compensation, allowing gradual increase in power transfer while preventing overload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the load is directly transferred to the engine-generator set, then the power transfer is fast, but the protective mechanisms trip due to transient overloading
Solution Approach 1:
The static switch operates in a dynamic manner, transitioning from fully off to fully on through intermediate conduction states. The control circuit dynamically adjusts the static switch's conduction angle or pulse width modulation (PWM) duty cycle, enabling gradual load transfer that prevents transient overloading while maintaining protective mechanism stability
Solution Approach 2:
The static switch is modulated using periodic control signals (such as PWM or phase-controlled triggering) that regulate the average power transferred to the load. This periodic modulation allows controlled incremental loading of the engine-generator set, preventing protective trips while achieving complete power transfer over time
2Reliability
If the load is gradually increased on the engine-generator set, then the protective mechanisms remain stable, but the power transfer speed decreases
Solution Approach 1:
The system dynamically adjusts the static switch conduction parameters to optimize the balance between transfer speed and generator protection. The control circuit monitors generator response and adapts the modulation depth and rate, enabling faster than traditional incremental transfer while maintaining protective stability
Solution Approach 2:
The control circuit changes operational parameters (conduction angle, PWM duty cycle, switching frequency) of the static switch to regulate power transfer rate. By dynamically adjusting these parameters, the system achieves optimized transfer speed that maintains generator stability while reducing overall transfer time compared to conventional methods
3Adaptability or versatility
If a double conversion UPS architecture is used, then generator walk-in is enabled, but the device complexity increases
Solution Approach 1:
The invention extracts the generator walk-in capability from the rectifier-inverter control system and implements it through a separate static switch modulation system. This separation allows generator walk-in functionality to be added to non-double-conversion UPS architectures without requiring the complex rectifier-inverter coordination of double conversion systems
Solution Approach 2:
The static switch serves as an intermediary device between the engine-generator set and the load, providing the walk-in capability without requiring complex integration into the existing UPS control architecture. This intermediary approach enables generator walk-in in simpler UPS configurations by adding a dedicated power modulation component rather than redesigning the entire control system
Data Source
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AI summary
An uninterruptible power supply (UPS) system includes an AC output, an inverter coupled to the AC output and configured to provide power at the AC output, and a switch configured to selectively couple a generator (e.g., an engine-generator set) to the AC output. The system further includes a control circuit configured to variably modulate the switch to gradually increase control power flow from the generator to the AC output while causing the inverter to concurrently provide power to the AC output. The switch may be a static switch that includes at least one silicon controlled rectifier (SCR), and the control circuit may be configured to control a conduction interval of the at least one SCR to control power flow from the generator to the AC output.